What is the recommended dosing for oseltamivir (Tamiflu) in liquid form?

Oseltamivir (Tamiflu) Liquid Dosing

Oseltamivir oral suspension is available at a concentration of 6 mg/mL and dosing varies by age, weight, and indication (treatment vs. prophylaxis), with specific volume measurements required for accurate administration. 1

Oral Suspension Formulation

• The commercially manufactured oral suspension provides a final concentration of 6 mg/mL after reconstitution by the pharmacist 1, 2
• If the commercial suspension is unavailable, pharmacies can compound a suspension using capsule contents mixed with simple syrup or Ora-Sweet SF to achieve the same 6 mg/mL concentration 3
• Administration with food may improve gastrointestinal tolerability, though it can be taken without food 1, 2

Treatment Dosing (5 days, twice daily)

Adults and Adolescents ≥13 years

• 75 mg twice daily = 12.5 mL twice daily for 5 days 1, 2

Children ≥12 months (weight-based)

• ≤15 kg (≤33 lb): 30 mg twice daily = 5 mL twice daily 1, 2
• >15-23 kg (>33-51 lb): 45 mg twice daily = 7.5 mL twice daily 1, 2
• >23-40 kg (>51-88 lb): 60 mg twice daily = 10 mL twice daily 1, 2
• >40 kg (>88 lb): 75 mg twice daily = 12.5 mL twice daily 1, 2

Infants <12 months (age-based, mg/kg dosing)

• 9-11 months: 3.5 mg/kg per dose twice daily 1, 4
• Term infants 0-8 months: 3 mg/kg per dose twice daily 1, 4
• For infants, use a dosing device that accurately measures small volumes (calculate: 0.5 mL per kg for 3 mg/kg dose, 0.58 mL per kg for 3.5 mg/kg dose) 2

Preterm Infants (postmenstrual age-based)

• <38 weeks postmenstrual age: 1.0 mg/kg twice daily 1
• 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily 1
• >40 weeks postmenstrual age: 3.0 mg/kg twice daily 1
• Consult pediatric infectious disease for extremely preterm infants <28 weeks 1

Prophylaxis Dosing (10 days, once daily)

Adults and Adolescents ≥13 years

• 75 mg once daily = 12.5 mL once daily for 10 days post-exposure 1, 2

Children ≥12 months (weight-based)

• ≤15 kg: 30 mg once daily = 5 mL once daily 1
• >15-23 kg: 45 mg once daily = 7.5 mL once daily 1
• >23-40 kg: 60 mg once daily = 10 mL once daily 1
• >40 kg: 75 mg once daily = 12.5 mL once daily 1

Infants 3-11 months

• 3 mg/kg once daily for 10 days 1, 5
• Prophylaxis is not recommended for infants <3 months unless the situation is judged critical due to limited safety data 1

Renal Impairment Adjustments

• Creatinine clearance 10-30 mL/min (treatment): 75 mg once daily (12.5 mL once daily) for 5 days instead of twice daily 1, 3
• Creatinine clearance 10-30 mL/min (prophylaxis): 30 mg once daily (5 mL once daily) for 10 days OR 75 mg every other day (12.5 mL every other day) for 10 days 1, 3
• Not recommended for end-stage renal disease patients not on dialysis 2

Critical Timing Considerations

• Treatment should be initiated within 48 hours of symptom onset for maximum benefit, reducing illness duration by approximately 1-1.5 days 5, 6
• Treatment initiated within 24 hours provides even greater benefit (37-40% reduction in illness duration) 6
• Prophylaxis should be started within 48 hours following close contact with an infected individual 5, 2
• Do not delay treatment in high-risk or hospitalized patients even if presenting beyond 48 hours, as mortality benefit persists 5

Common Pitfalls to Avoid

• Do not confuse treatment dosing (twice daily) with prophylaxis dosing (once daily)—this is a frequent prescribing error 3
• Ensure use of an appropriate oral dosing device that measures volume in mL, not household teaspoons 2
• For infants requiring mg/kg dosing, provide caregivers with a dosing device capable of measuring small volumes accurately 2
• Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use, and do not use oseltamivir for 14 days after LAIV vaccination 3
• The 30 mg unit dose may result in subtherapeutic exposures in some children aged 12-23 months; consider weight-based dosing in this age group 4